crisscross - we didn't do an 'official' route, because it suited us better to not. It was a nice route though, although the road through Hawes and Garsdale to Sedbergh isn't exactly the easiest and I wouldn't have taken the cub that way on a weekend, when the motorbikes are out in force. Adding a couple of train legs worked really well for us - I picked Bedale to Redmire because it took some hills out of the equation (and is a fabulous train journey!) and Arnside to Ulverston because I couldn't find a route down to Barrow that didn't involve either a big detour or some really nasty roads. 35+ miles with added hills on the second day was at the limit of what he could do with panniers on, and the 27annabit miles into the headwind and rain on the Friday was really testing stuff. He's really proud of what he achieved. There is talk of a tour down south, possibly at Easter, heading towards Hertford.... but since he hasn't done more than the school run since November he's need to get some miles in his legs first!
Edit to add...
one thing to do (worked for us anyway) in the build up is to make sure that, as well as a couple of day rides far in excess of what they'll need to do on tour, you get a couple of back to back days of riding in. The cub discovered that it's very different going out and doing 40 miles to doing 35 and then getting up the following day and doing it again! I also made it a condition of him going that he had to get his moving average consistently over 8mph on a day ride (his target is 1mph per year of his age - so I should be able to keep up for a couple more years!) which meant that even slowed down by hills and luggage we managed to keep it over 7mph apart from the really gruesome weather day - a speed that he couldn't maintain for more than 10 miles completely unladen when he started training at Easter. It wasn't the slightest bit important for us to get there fast - as you might notice, given the amount of tea, picnic and park stops we made - but the difference in the amount of time in the saddle at 5 or 6mph and at 8mph is significant!